Chrissie Wellington sucessfully defended the title she won last year. Photograph: Chris Stewart/AP

The British triathlete Chrissie Wellington broke the women's triathlon marathon record as she won a second consecutive Ironman world championship in Hawaii, confirming her as one of the dominant athletes in the discipline and proving that last year's shock win was no fluke.

"That was the hardest thing I've ever done," said the 31-year-old Wellington, who turned professional only eight months before she won last year's renewal of what is considered to be the world's toughest one-day endurance race. This year she beat her closest rival Yvonne Van Vlerken of Austria by close to 15 minutes, despite suffering mechanical issues with her bike.

After a 2.4-mile swim, Wellington went ahead of the field during 112-mile cycling stage and was five minutes clear when a flat tyre allowed the chasing pack to catch up. She was unable to re-inflate the tyre with her own air canisters, but received assistance from her rival Rebekah Keat of Australia. The repair cost Wellington 10 minutes but she was able to reclaim the time during the remainder of the cycling and her record-breaking run.

Wellington described Kent as "a legend" for her help and said the act of sportsmanship "epitomises everything great about the Ironman". Wellington's finishing time was 9hr 6min 23sec, including the 2hr 57min 44sec marathon.

The men's race was won by Craig Alexander of Australia.

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